Research On Element Diffusion And Bonding Breakage Of Cemented Carbide Tools Based On Molecular Dynamics

2.25Cr1Mo0.25 V material is widely used in petrochemical industry due to its high temperature resistance and corrosion resistance.The cemented carbide tools are commonly used in cutting 2.25Cr1Mo0.25 V material due to its high hardness and good thermal toughness.When the tool is cutting 2.25Cr1Mo0.25 V material,the element diffusion promotes the bonding behaviour between the tool and the chip to firmness,and the tool is prone to bonding damage,it is of great theoretical and practical significance to study on the diffusion law of tool chip elements by using Molecular Dynamics.The element diffusion of different tool materials are different under different temperature,which makes the degree of tool-chip bonding different.This paper is based on the National Natural Science Foundation(Project number: 51575146)"heavy cutting hard alloy face welding layer damage mechanism research".Based on the Molecular Dynamics method,the element diffusion law of different tool materials and workpiece materials at different temperatures were simulated,the tool-workpiece diffusion characteristics and bonding strength were studied,and the process and cause of bonding breakage were analyzed,in order to reduce the tool bonding breakage and improve the theoretical basis for cutting life.The specific research is organized as follows.The theory of Molecular Dynamics and its application in element diffusion were explored to provide the basis for diffusion simulation.According to Fick's second law,the diffusion model of each element was solved,and the conditions of element diffusion was analyzed by studying the diffusion mechanism of elements,the diffusion mechanism of different elements is obtained,which provides theoretical basis for the analysis and calculation of the following experiments.Based on Molecular Dynamics theory,three kinds of cemented carbide and 2.25Cr1Mo0.25 V material models were built by using Materials Studio software combining the process and microstructure of tool materials and workpiece materials,and the Molecular Dynamics simulation was proceeded.According to cutting experiments,the simulation temperature boundary conditions were determined,and the element diffusion situation of different tools and workpieces at different temperatures were obtained,the characteristics of tool-workpiece diffusion were analyzed,and the diffusion coefficient was calculated according to the model,the diffusion activities of each element were analyzed,the bonding properties between different tools and workpieces was obtained.The tool-workpiece clamping device was designed,and the tool-workpiece diffusion experiment scheme was formulated.The element content distribution situation of the diffusion interface is obtained by line scan analysis,the diffusion coefficients of the elements between different tools and workpiece materials at different temperatures were calculated by the diffusion equation.The diffusion law was analyzed.Comparing with the simulation results,the reliability of the simulation model was verified.The interfacial bonding energy of different tools under the action of temperature was calculated by the results of Molecular Dynamics simulation.Comparing with the bonding properties of different tools,the reason of tool-workpiece contact is explained based on the principle of interaction potential,the influence of the contact distance of tool-workpiece interface on the binding energy was analyzed.The process and causes of the tool bonding breakage were analyzed with comparsion of the binding energy before diffusion and binding energy after diffusion combining with the study on the crack in the tool-workpiece contact zone during the experiment.The preventive measure for reducing the bonding breakage was put forward.